Colloidal ordering from phase separation in a liquid-crystalline continuous phase

Some binary mixtures exist as a single phase at high temperatures and as tw o phases at lower temperatures; rapid cooling therefore induces phase separ ation that proceeds through the initial formation of small particles and su bsequent growth and coarsening(1). In solid and liquid media, this process leads to growing particles with a range of sizes, which eventually separate to form a macroscopically distinct phase. Such behaviour is of particular interest in systems composed of an isotropic fluid and a liquid crystal(2), where the random distribution of liquid-crystal droplets in an isotropic p olymer matrix may give rise to interesting electro-optical properties. Here we report that a binary mixture consisting of an isotropic fluid and a liq uid crystal forming the continuous phase does not fully separate into two p hases, but self-organizes into highly ordered arrays of monodisperse colloi dal droplet chains. We rnd that the size and spatial organization of the dr oplets are controlled by the orientational elasticity of the liquid-crystal phase and the defects caused by droplets exceeding a critical size. We exp ect that our approach to forming monodisperse, spatially ordered droplets i n liquid crystals will allow the controlled design of ordered composites th at may have useful rheological and optical properties.